My 2yo Has Flu Like Symptoms Since Thursday. Temp Range

My 2yo has flu like symptoms since Thursday. Temp range 100.7-103.1; never breaking the fever; gagging cough; runny nose; irritability and fatigue. No appetite except for pedialyte popsicles but now he doesn't even those and is not taking in much fluids either. I'm offering him anything and everything. Urgent care said he MAY have the Flu even though the nose swab came back negative. At what point do I take him to the ER?